SACRAMENTO, CA. - A drug used to treat diabetes encourages the brain to grow and repair itself, a finding with far-reaching implications for the treatment of Alzheimers and brain injury, a new study published in Cell: Stem Cell reports.

The widely used diabetes drug metformin comes with the unexpected side effect of causing the growth of new neurons in the brain and makes mice smarter, the July 6th issue of Cell Stem Cell, a Cell Press publication, said. The study has potentially wide-reaching implications for the treatment of Alzheimers in humans and brain related injury.

The discovery has important implications for brain repair because it works not by introducing new stem cells but rather by spurring those that are already present into action, said the study's lead author Freda Miller of the University of Toronto-affiliated Hospital for Sick Children. And since the drug is already so widely used and so safe it means doctors could quickly begin using the drug for brain therapy treatment.

Earlier work by Miller's team highlighted a pathway known as aPKC-CBP for its essential role in telling neural stem cells where and when to differentiate into mature neurons, the report said. Other researchers had found before them that the same pathway is important for the metabolic effects of the drug metformin, but in liver cells.

"We put two and two together," Miller says. If metformin activates the CBP pathway in the liver, they thought, maybe it could also do that in neural stem cells of the brain to encourage brain repairm, he said.

Mice taking metformin not only showed an increase in the birth of new neurons, but they proved to become smarter by being better able to learn the location of a hidden platform in a standard maze test of spatial learning. The new evidence lends support to that promising idea in both mouse brains and human cells.

While it remains to be seen whether the very popular diabetes drug might already be serving as a brain booster for those who are now taking it, there are early hints the drug may have cognitive benefits for people with Alzheimer's disease. Scientists had speculated those improvements were the result of better diabetes control, Miller says, but it now appears that metformin may improve Alzheimer's symptoms by enhancing brain repair.

Miller says they now hope to test whether metformin might help repair the brains of those who have suffered brain injury due to trauma or radiation therapies for cancer.